High-Resolution X-Ray Spectroscopy of the Evolving Shock in the 2006 Outburst of Rs Ophiuchi

Ness, J. U.; Drake, J. J.; Starrfield, S.; Bode, M. F.; O’Brien, T. J.; Evans, A.; Eyres, S. P. S.; Helton, L. A.; Osborne, J. P.; Page, K. L.; Schneider, Christian; Woodward, C. E.

doi:10.1088/0004-6256/137/2/3414

Cited by 58 publications

(86 citation statements)

References 63 publications

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“…Two recurrent novae with massive WDs of unknown composition were observed using gratings while they were relatively hard X-ray sources. RS Oph did not show very strong lines of Mg and Al, (Nelson et al 2008;Ness et al 2009), consistently with the ultraviolet spectra of a previous outburst (Contini et al 1995). V745 Sco was observed as a hard X-ray source with NuSTAR (Orio et al 2015) and shortly later it was observed it with the Chandra HETG.…”

Section: V959 Mon a Nova Discovered As A Gamma-ray Sourcesupporting

confidence: 85%

Chemical and Physical Parameters From X-Ray High-Resolution Spectra of the Galactic Nova V959 Mon

Peretz

Orio

Behar

et al. 2016

ApJ

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Two observations of V959 Mon, done using the Chandra X-ray gratings during the late outburst phases (2012 September and December), offer extraordinary insight into the physics and chemistry of this Galactic ONe nova. The X-ray flux was 1.7 × 10 −11 erg cm −2 s −1 and 8.6 × 10 −12 erg cm −2 s −1 , respectively at the two epochs. The first result, coupled with electron density diagnostics and compared with published optical and ultraviolet observations, indicates that most likely in 2012 September the X-rays originated from a very small fraction of the ejecta, concentrated in very dense clumps. We obtained a fairly good fit to the September spectrum with a model of plasma in collisional ionization equilibrium (CIE) with two components; one at a temperature of 0.78 keV, associated with flat-topped and asymmetrical emission lines, blueshifted by 710-930 km s −1 ; the other at a temperature of 4.5 keV, mostly contributing to the high-energy continuum. However, we cannot rule out a range of plasma temperatures between these two extremes; we also modeled the spectrum as a static cooling flow, but the available models and the data quality are not adequate yet to differentiate between the two-component fit and a smoothly varying temperature structure. In December, the central white dwarf (WD) became visible in X-rays. We estimate an effective temperature of 680,000 K, consistent with a WD mass ≥1.1 M . The WD flux is modulated with the orbital period, indicating high inclination, and two quasi-periodic modulations with hour timescales were also observed. No hot plasma component with temperature above 0.5 keV was observed in December, and the blueshifted component cooled to kT 0.45 keV. Additionally, new emission lines due to a much cooler plasma appeared, which were not observed two months earlier. We estimate abundances and yields of elements in the nova wind that cannot be measured in the optical spectra and confirm the high Ne abundance previously derived for this nova. We also find high abundance of Al, 230 times the solar value, consistently with the prediction that ONe novae contribute to at least 1/3rd of the Galactic yield of 26 Al.

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Section: V959 Mon a Nova Discovered As A Gamma-ray Sourcesupporting

confidence: 85%

Chemical and Physical Parameters From X-Ray High-Resolution Spectra of the Galactic Nova V959 Mon

Peretz

Orio

Behar

et al. 2016

ApJ

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“…This can be approximated by a multi-temperature model or by integration over a continuous temperature distribution. A comparison of these two approaches is presented by Ness et al (2009). The APEC model assumes solar abundances by Anders & Grevesse (1989) that can be scaled by a factor to determine an overall metallicity.…”

Section: Spectral Analysismentioning

confidence: 99%

XMM–Newton observation of MV Lyr and the sandwiched model confirmation

Dobrotka

Ness

Mineshige

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present spectral and timing analyses of simultaneous X-ray and UV observations of the VY Scl system MV Lyr taken by XMM-Newton, containing the longest continuous X-ray+UV light curve and highest signal-to-noise X-ray (EPIC) spectrum to date. The RGS spectrum displays emission lines plus continuum, confirming model approaches to be based on thermal plasma models. We test the sandwiched model based on fast variability that predicts a geometrically thick corona that surrounds an inner geometrically thin disc. The EPIC spectra are consistent with either a cooling flow model or a 2-T collisional plasma plus Fe emission lines in which the hotter component may be partially absorbed which would then originate in a central corona or a partially obscured boundary layer, respectively. The cooling flow model yields a lower mass accretion rate than expected during the bright state, suggesting an evaporated plasma with a low density, thus consistent with a corona. Timing analysis confirms the presence of a dominant break frequency around log(f /Hz) = -3 in the X-ray Power Density Spectrum (PDS) as in the optical PDS. The complex soft/hard X-ray light curve behaviour is consistent with a region close to the white dwarf where the hot component is generated. The soft component can be connected to an extended region. We find another break frequency around log(f /Hz) = -3.4 that is also detected by Kepler. We compared flares at different wavelengths and found that the peaks are simultaneous but the rise to maximum is delayed in X-rays with respect to UV.

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“…We first analysed the XMM-Newton observation taken on day 14 (ObsID 0410180101), which is not listed in Table 1 because it was not taken during the SSS phase; (Ness et al 2009). We divided the 23 ks observation into 46 overlapping 1000 s time segments but found no significant detection.…”

Section: Rs Ophmentioning

confidence: 99%

Short-period X-ray oscillations in super-soft novae and persistent super-soft sources

Ness

Beardmore

Osborne

et al. 2015

A&A

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Context. Transient short-period (<100 s) oscillations have been found in the X-ray light curves of three novae during their super-soft source (SSS) phase and in one persistent SSS. Aims. We pursue an observational approach to determine possible driving mechanisms and relations to fundamental system parameters such as the white dwarf mass. Methods. We performed a systematic search for short-period oscillations in all available XMM-Newton and Chandra X-ray light curves of persistent SSS and novae during their SSS phase. To study time evolution, we divided each light curve into short timesegments and computed power spectra. We then constructed a dynamic power spectrum from which we identified transient periodic signals even when only present for a short time. We base our confidence levels on simulations of false-alarm probability for the chosen oversampling rate of 16, corrected for multiple testing based on the number of time segments. From all time segments of each system, we computed fractions of time when periodic signals were detected. Results. In addition to the previously known systems with short-period oscillations, RS Oph (35 s), KT Eri (35 s), V339 Del (54 s), and Cal 83 (67 s), we found one additional system, LMC 2009a (33 s), and also confirm the 35 s period from Chandra data of KT Eri. The oscillation amplitudes are of about <15% of the respective count rates and vary without any clear dependence on the X-ray count rate. The fractions of the time when the respective periods were detected at 2σ significance (duty cycle) are 11.3%, 38.8%, 16.9%, 49.2%, and 18.7% for LMC 2009a, RS Oph, KT Eri, V339 Del, and Cal 83, respectively. The respective highest duty cycles found in a single observation are 38.1%, 74.5%, 61.4%, 67.8%, and 61.8%. Conclusions. Since fast rotation periods of the white dwarfs as origin of these transient oscillations are speculative, we concentrate on pulsation mechanisms. We present initial considerations predicting the oscillation period to scale linearly with the white dwarf radius (and thus mass), weakly with the pressure at the base, and luminosity. Estimates of the size of the white dwarf could be useful for determining whether these systems are more massive than typical white dwarfs, and thus whether they are growing from accretion over time. Signs of such mass growth may have implications for whether some of these systems are attractive as Type Ia supernova progenitors.

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High-Resolution X-Ray Spectroscopy of the Evolving Shock in the 2006 Outburst of Rs Ophiuchi

Cited by 58 publications

References 63 publications

Chemical and Physical Parameters From X-Ray High-Resolution Spectra of the Galactic Nova V959 Mon

Chemical and Physical Parameters From X-Ray High-Resolution Spectra of the Galactic Nova V959 Mon

XMM–Newton observation of MV Lyr and the sandwiched model confirmation

Short-period X-ray oscillations in super-soft novae and persistent super-soft sources

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